90 Cherokee problems and woes

I have a 90 cherokee laredo, today I pulled out the IAC and cleaned it off because it had alot of carbon build up. It still idles a little rough, what could be the problem? I also have a blow by problem, not a serious one though, only one end of the air filter gets covered with oil. I'm also leaking oil out my oil filler hole too, I've replaced the cap, PCV works great still sucks, could the hose be clogged? the Jeep has 200,000 miles on it. I'm thinking of going back to the conventional valvoline 10w-30 too, I've been using the max life 10w-30 synthetic. Would I run into any problems in doing this? I replaced my oil pan gasket and my rms over the summer. I still have a small oil leak, I'm guessing its because of the oil on top of the valve cover running down the back of the motor. Any response would be greatly appreciated.

any answers or suggestions would be greatly appreciated

megabyte5689 said:

I have a 90 cherokee laredo, today I pulled out the IAC and cleaned it off because it had alot of carbon build up. It still idles a little rough, what could be the problem? I also have a blow by problem, not a serious one though, only one end of the air filter gets covered with oil. I'm also leaking oil out my oil filler hole too, I've replaced the cap, PCV works great still sucks, could the hose be clogged? the Jeep has 200,000 miles on it. I'm thinking of going back to the conventional valvoline 10w-30 too, I've been using the max life 10w-30 synthetic. Would I run into any problems in doing this? I replaced my oil pan gasket and my rms over the summer. I still have a small oil leak, I'm guessing its because of the oil on top of the valve cover running down the back of the motor. Any response would be greatly appreciated.

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Try the following search terms for the rough idle:

Rough idle Renix

Also look for tune up threads on plugs, wires, fuel injectors, seafoam, and loose / bad ground wires to start with. Even check the battery cables.

Lots of possible causes for a rough idle, bad plug(s), bad plug wire(s), bad or dirty fuel injector(s), bad valve(s), a bad head gasket, low compression on one or more cylinders, bad fuel regulator, the trick is to figure out what is bad and what is not. Some kinds of vacuum leaks can cause idle problems too like an intake gasket leak.

On the oil leak I would change the valve cover gasket and get ready to change the oil filter adapter o'rings ( search "renix oil filter adapter o'ring" )
also search for details on the CCV line replacement, search for "crank case ventilation", the small tube gets pluged and the valve cover gasket and top seals leak air in and cause the oil to get blown, or actually sucked backwards into the air filter assy. Replace the small CCV line and rubber gaskets and valve cover gasket on the valve cover to stop the oil on air filter problem and the other oil leaks. The oil filter adapter o'ring is the last place to reseal. It mimicks a rear seal leak. Oh, and the Jeep does does not use a PCV valve, it uses a Crank Case Ventilation hose system, CCV.

Check to see that the rear hose connecting the valve cover to the intake manifold isn't plugged with crud. This will help stop oil from soaking the filter.
If the engine is properly tuned up (plugs, wires, cap, rotor, fuel filter) a possible leaking EGR valve will contribute to a rough idle.

Slo-Sho said:

Check to see that the rear hose connecting the valve cover to the intake manifold isn't plugged with crud. This will help stop oil from soaking the filter.
If the engine is properly tuned up (plugs, wires, cap, rotor, fuel filter) a possible leaking EGR valve will contribute to a rough idle.

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True but there is no EGR valve on the 90 model.

Ecomike said:

True but there is no EGR valve on the 90 model.

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On every single Renix 4.0l I've ever seen there is a EGR valve on the side of the intake manifold with a tube running up from the exhaust manifold. May I ask what 90 Renix did not have an EGR?

Slo-Sho said:

On every single Renix 4.0l I've ever seen there is a EGR valve on the side of the intake manifold with a tube running up from the exhaust manifold. May I ask what 90 Renix did not have an EGR?

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Old age, mad cow disease, memory loss perhaps, :banghead:I thought I remembered reading the EGR elimination around 89 in the renix era, but my searches seem to favor 91, HO, OBD-I as the actual year the EGR was elliminated. My mistake, he needs to check the EGR for the rough idle too. Good catch!

I replaced plugs, cap & rotor, plug wires, ignition coil, ignition switch since I've owned the vehicle. Fuel filter has been replaced too, I'm sure the injectors aren't clogged, because it gets really bad idle after its been running, I shut it off and then start it back up is when it gets really worse, it died yesterday after I did this. how many egr valves are there? I saw two parts that look exactly the same, I know one of them is the egr valve.

It's the round thing.

megabyte5689 said:

I replaced plugs, cap & rotor, plug wires, ignition coil, ignition switch since I've owned the vehicle. Fuel filter has been replaced too, I'm sure the injectors aren't clogged, because it gets really bad idle after its been running, I shut it off and then start it back up is when it gets really worse, it died yesterday after I did this. how many egr valves are there? I saw two parts that look exactly the same, I know one of them is the egr valve.

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Just 1, it is bolted to the side of the intake manifold, it's metal, it has a tube about 3/4" diamter exiting the bottom side that attaches to the exhaust pipe end of the exhaust manifold. It is attached to an electric solenoid valve and a transducer (if yours has the transducer) via vacuum lines.